In a Long Term Evolution (LTE)/Long Term Evolution Advanced (LTE-A) communications system, an orthogonal frequency division multiple access (OFDMA) manner is usually used as a downlink multiple access manner. A main characteristic of the orthogonal frequency division multiple access manner is that different users use different time-frequency resources to ensure that there is no interference between signals received by different users, so as to achieve simple reception on a user side. However, when the orthogonal frequency division multiple access manner is used for communication, utilization of a time-frequency resource is relatively low, and consequently, an overall transmission rate of the communications system is limited.
In a non-orthogonal multiple access (NOMA) transmission manner, information of multiple users can be transmitted on a single resource element (RE). Compared with the OFDMA, the NOMA improves an overall transmission rate of a system. In a NOMA technology, transmission signals of multiple users are superimposed in a time-frequency domain, and different power is allocated to different users to ensure accurate reception on the user side. On a reception side, a cell-edge user or a user relatively far from a base station treats a signal of a cell-center user as interference, so as to achieve accurate demodulation. The cell-center user or a user relatively close to the base station needs to first detect a signal of the cell-edge user, then use an interference cancellation algorithm, and finally accurately demodulate a signal of the cell-center user or the user relatively close to the base station.
However, according to a communications technology based on the NOMA, more downlink control parameters need to be transmitted, and signaling overheads are larger.